1. Field of the Invention
The present invention relates to a vibration gyroscope and an electronic device including the vibration gyroscope.
2. Description of the Related Art
A pillar-shaped vibrator that performs bending vibration with both ends open, which is used in a vibration gyroscope, is supported such that the vicinity of the nodes is fixed to supporting members. Then, the needle-shaped supporting members are arranged such that the vibration of the vibrator is not disturbed.
When an external impact force is applied to a vibrator supported by such supporting members, although the vibrator is inclined to be displaced, the vibrator is supported by the elastically deformed supporting members. Therefore, after the impact force subsides, the supporting members return to their original state.
However, when the magnitude of the impact force exceeds a fixed value, the deformation of the supporting members exceeds the range of elastic deformation and plastic deformation takes place, and accordingly, after the impact force subsides, the supporting members do not return to their original state. Once plastic deformation of the supporting members occurs, the position of the vibrator changes and there is a problem that a normal angular velocity cannot be detected.
In order to avoid such a problem, a stopper has been provided for restricting displacement of the vibrator beyond a fixed distance due to an excessive impact force. The construction including a stopper is disclosed in Japanese Unexamined Patent Application Publication No. 6-201386, Japanese Unexamined Patent Application Publication No. 6-331363, Japanese Unexamined Patent Application Publication No. 7-208997, Japanese Unexamined Patent Application Publication No. 8-159779, and Japanese Unexamined Patent Application Publication No. 9-159455. That is, in each of the references cited above, a stopper is arranged so as to enclose both end portions of a pillar-shaped vibrator and, in this way, displacement of the vibrator beyond a fixed level is prevented and plastic deformation of the supporting members is prevented.
However, when the above-described stopper is provided, since the number of parts increases and the assembly time also increases in the manufacturing process, there is a problem that the cost of a vibration gyroscope greatly increases.
In order to overcome the above-described problems, preferred embodiments of the present invention provide a vibration gyroscope and an electronic device including the vibration gyroscope in which, although a stopper portion is provided, the cost of the vibration gyroscope is not substantially increased.
A vibration gyroscope according to preferred embodiments of the present invention includes a base having a hollow portion, supporting members fixed to the base, and a vibrator supported by the supporting members in the hollow portion of the base. The base includes a frame portion, and a stopper portion provided on the inner wall of the frame portion so as to limit displacement of the vibrator within a desired distance, and the frame portion and the stopper portion are integrally formed to define a single unitary member.
Furthermore, in a vibration gyroscope according to preferred embodiments of the present invention, the stopper portion is preferably defined by a thick wall portion or a protrusion portion provided on the inner wall of the frame portion of the base. The stopper portion is preferably elastic.
The frame portion and the stopper portion of the base are preferably formed by integrally molding two materials to define a single unitary member including the frame portion and the stopper portion.
Preferably, the vibration gyroscope according to preferred embodiments of the present invention further includes sandwiching members arranged above and below the hollow portion of the base to sandwich the base. The sandwiching members are preferably defined by a circuit substrate or a case and define a second stopper portion to limit displacement of the vibrator in the thickness direction of the base.
Furthermore, an electronic device according to preferred embodiments of the present invention includes the vibration gyroscope according to preferred embodiments described above.
With the vibration gyroscope according to preferred embodiments of the present invention, the plastic deformation of the supporting members and the damage of the vibrator caused by an impact force is effectively prevented while using fewer parts. Thus, the cost of manufacturing the vibration gyroscope is greatly reduced while the performance thereof is greatly improved.
Furthermore, in the electronic device according to preferred embodiments of the present invention, the reliability of detection of an angular velocity caused by an impact force is greatly improved.
The features, elements, characteristics and advantages of the present invention will be clear from the following detailed description of preferred embodiments of the invention in conjunction with the accompanying drawings.